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POPULAR SCIENCE REVIEW. 
with dip, strike, and faulting of rocks, and their curvatures, contortions, and 
cleavage, the nature of igneous and metamorphic rocks and mineral veins, 
with a chapter on surface geology as connected with physical features. 
The second part treats of the nature of indoor work, as drawing geological 
sections, hints for the determination of minerals and rocks, and the method 
of preparing sections for investigation by the microscope. The drawing of 
geological sections is of much importance, considering how frequently false 
ideas are given by diagrammatic representations of the external form of the 
ground, thus tending to perpetuate erroneous notions with regard to the 
physiography of the land as shown by such distorted sections, sometimes 
almost grotesque in their exaggeration of natural fora: s. Similar erroneous 
notions apply to some drawings of unconformable stratification. We can cor- 
roborate Professor Geikie in his remarks on this structure, having recently 
seen drawings of much more impossible unconformities than even that given 
by him at page 113. 
W T e may notice among the few typographical errors the letters a c of the 
woodcut, fig. 29, which are wrongly described, indicating an inversion of the 
strata, which is not the case, as shown by reference to the original figure 
(174), from which it is taken in the " Geological Observer.” At p. 109 is 
described a ready means of estimating the thickness of strata, which appears 
more simple than that proposed by Professor Chapman. In this paragraph 
the author might have usefully alluded to the method of calculating the 
depth from the surface at which an inclined stratum might be reached at a 
given distance from the nearest outcrop. 
To the geological student who is acquainted merely with the principles of 
the science derived only from book-study, this concisely arranged and 
pleasantly- written text-book by Professor Geikie, for guidance in the field, 
will be a valuable aid, as pointing out how and what to observe and how 
to record, thus adding fresh interest to his studies, and ministering to his 
further elevation and enjoyment, by a more practical knowledge of the 
nature of the district in which he finds himself situated, or into which the 
pursuit may lead him. 
FRAGMENTS OF SCIENCE.* 
W E need do little more than announce the publication of a new and 
enlarged edition of Professor Tyndall’s “ Fragments of Science.” 
Deservedly recognized as one of our most brilliant writers on subjects con- 
nected with physical science, Professor Tyndall has the art of investing 
with a peculiar charm matters which at first sight might seem rather un- 
promising, while at the same time he is a most lucid popular expositor of 
scientific facts and theories. These circumstances make it no matter of 
wonder that the collection of essays, reviews, lectures, and addresses which 
he brought out a few years ago under the above title should have already 
arrived at a sixth edition. Of course, there are portions of these articles at 
* 11 Fragments of Science.” A Series of Detached Essays, Addresses, and 
Reviews. By John Tyndall, F.R.S. Sixth edition. 2 vols. Crown 8vo. 
London : Longmans & Co., 1879. 
